Voltage to current conversion circuit including a differential amplifier

摘要

An accurate V/I conversion circuit converts an input voltage to an electric current which includes an external resistance in series with an input voltage V1. The external resistance is directly coupled to an input terminal of the V/I conversion circuit. V/I conversion circuit includes an input terminal coupled to the external resistance which is in series with the input voltage V1. V/I conversion circuit also includes (1) a resistance type voltage dividing circuit which generates a standard voltage by dividing a supply voltage, (2) a differential amplifier circuit comprising two transistors which compares a voltage of the input terminal with the standard voltage, (3) a third transistor which receives the collector voltage of one of the transistors in the differential amplifier where the third transistor is also connected between the input terminal and ground with a resistor in series, and (4) a fourth transistor which receives a collector voltage of one of the transistors of the differential amplifier. The fourth transistor is also connected between the supply voltage and the ground with a resistance in series. The output current flows through the fourth transistor. The V/I conversion circuit can be formed in an integrated circuit.